Question

In isoelectronic species ${\mathrm{Cl}}^{-},\mathrm{Ar},{\mathrm{Ca}}^{+2}$ size differ due to

• A. Nuclear charge
• B. Electronic-electronic repulsion in valence shell
• C. magnetic quantum number
• D. Principal quantum number

Answer 1

The correct option is A

Nuclear charge

The correct option is option A

The explanation for the correct option:

1. Isoelectronic species are those that are part of different atoms or ions and have the same number of electrons but different nuclear charge value
2. For iso-electronic species, the proton to electron ratio, or $\left(\frac{\mathrm{p}}{{\mathrm{e}}^{-}}\right)$ratio, controls the size.
3. As the value of the (Pe) ratio increases, the size of the ion will decrease because more number of proton will have a stronger ability to hold electrons.
4. Therefore, we can conclude that nuclear charge, or the number of protons, has an effect on size.

The explanation for the incorrect options:

Option (B): Electronic-electronic repulsion in the valence shell

1. As all isoelectronic species have the same number of electrons, electron-electron interaction in the outer orbitals has no effect on size.
2. Hence, it is an incorrect option.

Option (C): Magnetic quantum number

1. The magnetic quantum number principally determines the number and direction of orbitals in a specific electron subshell
2. It has no relation to the size of isoelectronic species.
3. Hence, it is an incorrect option.

Option (D): Principal quantum number

1. The principal quantum number is given by n, which roughly specifies the size of the electron orbital.
2. A higher value of the primary quantum number denotes a farther distance between the nucleus and the electrons, which indicates how far the nucleus and electrons are likely to be separated.
3. It has no relation to the size of isoelectronic species.
4. Hence, it is an incorrect option.

Final answer: In isoelectronic species ${\mathrm{Cl}}^{-},\mathrm{Ar},{\mathrm{Ca}}^{+2}$ size differ due to nuclear charge